The present invention relates to the field of hydraulic units, such as pumps and motors. More particularly, this invention relates to a means and method for sealing an irregularly shaped cavity in the housing of a hydraulic unit, such as an open circuit axial piston pump.
Conventional open circuit axial piston pumps often have an irregularly shaped (non-circular) cavity in the housing for receiving the cylinder block kit or pumping portion of the unit, as well as the servo piston and bias piston that position the swashplate to establish the fluid displacement of the unit. Although the required cavity has a large circular central portion for accommodating the cylinder block kit, opposite ear-like portions extend outwardly to accommodate the bias piston and servo piston respectively. Since the overall cavity is irregular or non-circular, use of an O-ring with a circular overall shape tends to increase the size of the housing and therefore undesirably increases the package size of the hydraulic unit. Gaskets have been tried to seal the area around the irregular cavity, but the leakage potential is often undesirably high, especially when the package size requirements do not allow a sufficiently large effective gasket sealing area. The shortcomings of gaskets have lead some pump manufacturers to use molded O-rings to face seal the non-circular area. However, due to the high cost of molds and tooling, molded O-rings are relatively expensive. This is especially true if a non-circular cross-section O-ring is desired. Thus, there is a need for an improved means and method for sealing the irregularly shaped housing cavity of a hydraulic unit.
Therefore, a primary objective of the present invention is the provision of an improved means and method for face sealing around an irregularly shaped cavity.
A further objective of this invention is the provision of a face sealing ring and groove arrangement that can be produced with low-cost lathe operations instead of more expensive molding and milling operations.
Another objective of this invention is the provision of a single lathe cut face seal for sealing the irregular area between the housing and end cap of a hydraulic pump.
Another objective of the present invention is the provision of a lathe cut sealing ring that has a rectangular cross-section and positioning ribs on its inside diameter for better retention and pressure containment.
These and other objectives will be apparent from the drawings, as well as from the description and claims that follow.
The invention relates to a means and method for sealing an irregularly shaped cavity in a hydraulic unit. A sealing ring includes a substantially cylindrical ring of elastomeric material formed about a central axis. The ring has a rectangular cross-section, opposite planar upper and lower surfaces defining a nominal axial thickness therebetween, and an outer diameter and an inner diameter with a ring axis centrally located therebetween. The inner diameter has a plurality of angularly or circumferentially spaced positioning ribs formed thereon and protruding inwardly therefrom. The ribs have an arcuate profile in a plane perpendicular to the central axis. Advantageously, the sealing ring of this invention and the groove into which it fits, can be formed by lathe cutting operations. Thus, a reliable and cost-effective face sealed joint can be provided. The method of providing such a joint is also disclosed herein.